CN113750988B - Heterogeneous junction manganese oxide catalyst and preparation method and application thereof - Google Patents
Heterogeneous junction manganese oxide catalyst and preparation method and application thereof Download PDFInfo
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- 229910021642 ultra pure water Inorganic materials 0.000 claims description 4
- 239000012498 ultrapure water Substances 0.000 claims description 4
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- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 abstract description 137
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- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 description 8
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/32—Manganese, technetium or rhenium
- B01J23/34—Manganese
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8668—Removing organic compounds not provided for in B01D53/8603 - B01D53/8665
-
- B01J35/61—
Abstract
The invention discloses a heterogeneous junction manganese oxide catalyst and a preparation method and application thereof, and belongs to the technical field of catalytic materials. The manganese oxide catalyst consists of amorphous manganese oxide and alpha-MnO 2 Composition, homogeneous heterogeneous phase junction into amorphous phase manganese oxide and alpha-MnO 2 Is a phase interface of (c). The invention induces delta-MnO by a mechanical method 2 Conversion to alpha-MnO 2 The phase transition process is subjected to an amorphous mesophase, the obtained amorphous manganese oxide and alpha-MnO 2 And constructing synergistic catalytic active sites in a combined way. The invention provides a synthetic method for constructing a homogeneous heterogeneous catalyst, which has the advantages of easily available raw materials, simple and convenient operation and convenient mass production. The prepared catalyst is applied to a formaldehyde catalytic oxidation system, has high intrinsic performance and rich active sites, can efficiently and stably realize complete catalytic decomposition of formaldehyde at 80 ℃, and has activity superior to most of currently reported manganese-based non-noble metal catalysts.
Description
Technical Field
The invention belongs to the technical field of catalytic materials, and particularly relates to a heterogeneous junction manganese oxide catalyst and a preparation method and application thereof.
Background
Formaldehyde is one of the most serious indoor air pollutants, and is the most prominent hazard to human health. Because the compound has high chemical reactivity with biomass such as protein in the body to cause the denaturation of the biomass, the compound can cause a series of respiratory diseases such as nasosinusitis, sphagitis, bronchitis, asthma and the like when being exposed to formaldehyde environment with an exceeding concentration for a long time, and even cause canceration and leukemia in serious cases. Therefore, the research and development of safe and efficient formaldehyde purification and elimination technology has important significance. Compared with other purification technologies, the catalytic oxidation method is regarded as the most promising formaldehyde elimination technology due to the advantages of environmental friendliness, simple equipment, no secondary pollutants, strong universality and the like. The development of a safe and efficient formaldehyde oxidation catalyst is a key for the practical application of the technology for promoting catalytic oxidation to eliminate formaldehyde.
The key point of the catalytic oxidation technology is the selection of the catalyst, and the catalyst can be divided into a supported noble metal catalyst and a non-noble metal catalyst (transition metal catalyst) according to the difference of the main materials of the catalyst. The supported noble metal catalyst represented by Pt, au, pd, ag, etc. has excellent reactivity, and can achieve complete oxidation of formaldehyde at low temperature even at room temperature. However, the high price of noble metals has limited the wide application of such catalysts, and how to develop a high-efficiency and low-cost catalyst has become a research focus. Thus with a transition metal catalyst (MnO) 2 、CeO 2 、Co 3 O 4 Etc.) are receiving a great deal of attention. In recent years, the design of a catalyst material that improves the catalytic activity of a non-noble metal catalyst to obtain an application value has become a mainstream trend of developing a formaldehyde catalytic oxidation technology. According to literature reports, the modification of non-noble metal catalysts mainly focuses on component modulation and structural optimization, and strategies such as doping and compounding, structural nanocrystallization, morphology control, defect modulation and the like are often adopted. However, in general, the non-noble metal catalyst still has the problems of low activity, poor long-term working stability, poor moisture resistance and the like, so the design concept and the controllable synthesis method of the non-noble metal catalyst with high activity still have key problems to be solved in the progress of promoting the practical application of formaldehyde catalytic oxidation technology.
Disclosure of Invention
In view of the above drawbacks and deficiencies of the prior art, a primary object of the present invention is to provide a heterogeneous junction manganese oxide catalyst. The catalyst of the invention has the characteristics of a large number of heterogeneous phase interfaces and oxygen vacancies enrichment, and has high intrinsic catalytic activity and rich active sites.
Another object of the present invention is to provide a method for preparing the heterogeneous junction manganese oxide catalyst. The invention adopts a two-step method of combining hydrothermal treatment and ball milling treatment. Firstly, taking aqueous solution containing potassium permanganate and manganese salt asThe metastable phase delta-MnO is prepared from the initial raw material by a hydrothermal method 2 The precursor is subjected to ball milling to induce phase change (delta-MnO) 2 Conversion to alpha-MnO 2 The phase change process is subjected to amorphous intermediate phase), and a manganese oxide catalyst with homogeneous heterogeneous junction is obtained by selecting proper ball milling conditions. The method has the advantages of easily available raw materials, simple and convenient operation and convenient mass production, and makes industrial production possible.
It is still another object of the present invention to provide the use of the heterogeneous manganese oxide catalyst in formaldehyde catalytic oxidation, which can efficiently and stably catalyze formaldehyde oxidative decomposition at 80 ℃ and has activity superior to most of the manganese-based non-noble metal catalysts reported so far.
The aim of the invention is achieved by the following technical scheme.
A heterogeneous junction manganese oxide catalyst consisting of an amorphous phase manganese oxide and alpha-MnO 2 Composition of the amorphous manganese oxide and alpha-MnO 2 The phase interface of (C) is a homogeneous heterogeneous junction.
Preferably, the manganese oxide refers to non-noble metal oxide MnO with polymorphism 2 。
Preferably, the homoheterogeneous junction interface is rich in oxygen vacancies.
The preparation method of the heterogeneous junction manganese oxide catalyst, which comprises the following steps:
MnO is added to 2 Ball milling is carried out in an air atmosphere to prepare the heterogeneous manganese oxide catalyst; the MnO 2 Is delta-MnO 2 。
Preferably, the ball milling time is 0.5-20 h.
Preferably, the rotation speed of the ball mill is 50-1200 rpm.
Preferably, the ball-milling ball-material ratio is 10:1-200:1.
Preferably, the ball milling time is 3 hours; the rotation speed of the ball milling is 600rpm; the ball-milling ball-material ratio is 100:1.
Preferably, in the ball milling process, the ball mill is at least one of a planetary ball mill, a shimmy ball mill and a vibrating plasma ball mill, and the ball milling tank and the grinding balls are at least one of stainless steel, agate, zirconia and polytetrafluoroethylene materials.
Preferably, the delta-MnO 2 The preparation of the composition comprises the following steps:
dissolving potassium permanganate and manganese salt in water, performing hydrothermal reaction after ultrasonic and stirring, cooling to room temperature after the reaction is completed, and cleaning and drying the obtained precipitate to obtain delta-MnO 2 。
Preferably, the manganese salt refers to MnSO 4 、Mn(NO 3 ) 2 、MnCO 3 、Mn(CH 3 COO) 2 At least one of (a) and (b); the ultrasonic time is 1-2 hours; the stirring time is 0.5-2 hours; the cleaning is to clean with ultrapure water and absolute ethyl alcohol respectively; the concentration of the potassium permanganate added into water is 0.012-0.03M, and the concentration of the manganese salt added into water is 0.002-0.005M; the temperature of the hydrothermal reaction is 140-180 ℃ and the time is 8-16 h.
Preferably, the hydrothermal reaction temperature is 160 ℃; the time is 6-12 h.
The use of a heterogeneous junction manganese oxide catalyst as defined in any one of the preceding claims in the catalytic oxidation of formaldehyde.
The principle of the invention is as follows: for formaldehyde catalytic oxidation catalysts, the adsorption capacity of the catalyst for formaldehyde molecules and the activation capacity for oxygen molecules are key to influencing the catalytic performance. The existing non-noble metal catalyst is difficult to realize low-temperature catalytic oxidation of formaldehyde due to weak formaldehyde molecule adsorption capability or difficulty in continuously generating active oxygen. The catalyst provided by the invention introduces the synergistic effect of heterogeneous junction in the design thought to optimize the two aspects of formaldehyde molecule adsorption and active oxygen generation, and provides a simple and easy preparation method for implementation. The invention synthesizes the manganese oxide catalyst with homogeneous heterogeneous junction by adopting a hydrothermal combined ball milling two-step method. Firstly, obtaining metastable phase precursor delta-MnO which is easy to generate phase change through a hydrothermal method 2 The method comprises the steps of carrying out a first treatment on the surface of the And then, the catalyst with homogeneous heterogeneous phase nodes is obtained by regulating and controlling ball milling conditions. The obtained amorphous manganese oxide and alpha-phase manganese dioxide are combined to construct the synergistic catalytic activitySex sites wherein the amorphous manganese oxide phase provides active sites for decomposing oxygen molecules to produce reactive oxygen species, and the alpha phase manganese dioxide provides formaldehyde adsorption sites. In the invention, the lattice height of the heterogeneous junction interface is not matched, so that the heterogeneous junction interface has a rich defect structure; in addition, the mechanical action can further increase the oxygen defect content of the catalyst. The amorphous manganese oxide and alpha-phase manganese dioxide are combined to construct homogeneous heterogeneous junction and combine rich oxygen vacancies, so that a large number of active sites and adsorption sites are provided for formaldehyde catalytic oxidation, and the activity of formaldehyde catalytic oxidation is synergistically improved. In summary, the formaldehyde catalytic oxidation catalyst provided by the invention has high intrinsic activity and rich active sites.
Compared with the prior art, the invention has the following advantages:
(1) The method and the material provided by the invention have the advantages of effectively optimizing the intrinsic activity and the number of active sites. A large number of oxygen vacancies are effectively introduced by constructing homogeneous heterogeneous junctions to form a large number of phase interfaces, and the obtained amorphous manganese oxide and alpha-phase manganese dioxide are combined to construct a synergistic catalytic active site, so that the catalyst activity and catalytic stability are effectively improved.
(2) The preparation method has the advantages of easily available raw materials, simple process and convenient mass production, and enables industrial production to be possible.
(3) The manganese oxide catalyst obtained by the invention can realize complete oxidation removal of formaldehyde at 80 ℃ and has higher specific surface area reaction rate (up to 0.21 mu mol m) -2 min -1 ) The method comprises the steps of carrying out a first treatment on the surface of the In addition, it exhibits excellent stability, and its activity is superior to most of the currently reported manganese-based non-noble metal catalysts.
Drawings
FIG. 1 shows precursor delta-MnO in example 1 of the present invention 2 alpha/A-MnO of target catalyst 2 -3 and reference sample alpha-MnO 2 -3 and A-MnO 2 X-ray diffraction pattern of (2); wherein 3 refers to the ball milling time (h).
FIG. 2 shows the target catalyst α/A-MnO obtained in example 1 of the present invention 2 -transmission electron microscope topography of 3 (a); a selected area electron diffraction pattern (b) and a high resolution transmission electron micrograph (c).
FIG. 3a shows the target catalyst α/A-MnO obtained in example 1 of the present invention 2 -3X-ray photoelectron spectroscopy in the O1s region.
FIG. 3b shows the target catalyst α/A-MnO obtained in example 1 of the present invention 2 -3X-ray photoelectron spectroscopy in the Mn 2p region.
FIG. 3c shows the target catalyst α/A-MnO obtained in example 1 of the present invention 2 -3X-ray photoelectron spectroscopy in the Mn 3s region.
FIG. 4 shows the precursor delta-MnO obtained in example 1 of the present invention 2 alpha/A-MnO of target catalyst 2 -3 and reference sample alpha-MnO 2 -3 and A-MnO 2 Formaldehyde catalytic oxidation performance graph of (a).
FIG. 5 shows the target catalyst α/A-MnO obtained in example 1 of the present invention 2 -3 stability test results graph.
FIG. 6 shows a series of catalysts alpha/A-MnO obtained by different ball milling times in example 2 of the present invention 2 -X-ray diffraction pattern of T; wherein T refers to ball milling time (h).
FIG. 7 shows a series of catalysts alpha/A-MnO obtained by different ball milling times in example 2 of the present invention 2 -formaldehyde catalytic oxidation profile of T.
FIG. 8 shows the alpha/A-MnO catalysts of the present invention obtained in example 3 at different ball to material ratios 2 -X-ray diffraction pattern of R; wherein R refers to the ball-to-material ratio.
FIG. 9 shows a series of catalysts alpha/A-MnO obtained in example 3 of the present invention at different ball to material ratios 2 -formaldehyde catalytic oxidation profile of R.
FIG. 10 shows the MnO of different crystal forms in comparative example 1 of the present invention 2 X-ray diffraction pattern of the catalyst obtained after ball milling treatment.
FIG. 11 shows the MnO of different crystal forms in comparative example 1 of the present invention 2 And (3) carrying out ball milling treatment to obtain the formaldehyde catalytic oxidation performance diagram of the catalyst.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the embodiments and the scope of the present invention are not limited thereto.
Example 1
(1) And (3) preparing a catalyst:
preparing precursor delta-MnO by adopting a hydrothermal method 2 The method comprises the following specific steps of: 15.0mmol KMnO 4 、2.5mmol MnSO 4 Dispersing in 120mL of ultrapure water, sequentially carrying out ultrasonic treatment, stirring for 1 hour, placing into a polytetrafluoroethylene reaction kettle with the volume of 200mL, carrying out constant-temperature reaction at 160 ℃ for 12 hours, naturally cooling to room temperature, fully cleaning the obtained precipitate (respectively cleaning with ultrapure water and absolute ethyl alcohol), and drying to obtain precursor delta-MnO 2 。
α/A-MnO 2 -3 preparation of heterogeneous catalyst: and ball milling is adopted to prepare the target catalyst. Specifically, 0.1g of the obtained delta-MnO by hydrothermal reaction was charged in an agate tank 2 The ball-to-material ratio is 100:1. Precursor delta-MnO using planetary ball mill 2 Ball milling for 3 hours at 600rpm to obtain the target catalyst.
Reference sample alpha-MnO 2 -3 preparation: the material is prepared by adopting a hydrothermal combination ball milling method. Wherein hydrothermal method and precursor sample delta-MnO 2 The preparation method is similar and differs in KMnO 4 And MnSO 4 The molar ratio is 6:1 is changed to 2.5:1, other than the above, are the same to obtain alpha-MnO 2 . Subsequently, alpha-MnO is added 2 The samples were processed under ball milling conditions consistent with the target catalyst to produce reference samples.
Reference sample amorphous manganese oxide (designated A-MnO) 2 ) Is prepared from the following steps: adding delta-MnO obtained by hydrothermal reaction into an agate tank 2 And 0.01g of graphene oxide, and the rest ball milling conditions are consistent with those of the target catalyst, so as to prepare a reference sample.
(2) Characterization of the phase/structure/elemental chemistry of the catalyst:
the catalyst obtained in this example was alpha/A-MnO 2 The X-ray diffraction and selective electron diffraction patterns of-3 are shown in fig. 1 and b of fig. 2, respectively. Combining XRD and selected area electron diffraction analysis proves that delta-MnO 2 Finally converted into alpha-MnO under the action of mechanical force 2 The phase change process is subjected to amorphous intermediate phase, and the prepared catalyst alpha/A-MnO 2 -3 containing amorphous manganese oxide and alpha-MnO 2 And forming a phase interface. High resolution transmission electron microscope observation(see c in FIG. 2) further demonstrates the presence of an amorphous phase/alpha phase out-of-phase junction. Transmission electron microscopy (see a in fig. 2) revealed that the milled samples were irregularly granular.
According to X-ray photoelectron spectroscopy analysis (see FIG. 3a, FIG. 3b and FIG. 3 c), the obtained target catalyst alpha/A-MnO 2 -3 shows that the catalyst surface has a plurality of oxygen vacancies; in addition, both Mn 2p and 3s spectra demonstrate the presence of Mn in the corresponding low valence state 3+ The signal further confirms that oxygen vacancies exist on the surface of the catalyst.
(3) The catalyst obtained in this example was alpha/A-MnO 2 -3 catalytic performance test:
target catalyst and precursor delta-MnO at different temperatures 2 alpha-MnO of reference sample 2 -3 and A-MnO 2 The change in catalytic activity of-3 (see FIG. 4) indicates that alpha/A-MnO 2 The catalyst-3 has excellent catalytic activity, and can completely catalyze and oxidize 120ppm of formaldehyde into CO at 80 DEG C 2 And H 2 O, which indicates that it has excellent low temperature catalytic activity. The activity of the catalyst is superior to that of most of the currently reported manganese-based non-noble metal catalysts. Formaldehyde catalytic oxidation reaction conditions: the raw material is a mixture of 120ppm formaldehyde and high-purity air, and the gas volume space velocity is 200L g cat -1 h -1 。
FIG. 5 shows alpha/A-MnO 2 And 3, the stability test result of the catalyst shows that the catalyst activity is not degraded after 24 hours of isothermal (80 ℃) test, thus the catalyst has excellent stability. Formaldehyde catalytic oxidation reaction conditions: the raw material is a mixture of 120ppm formaldehyde and high-purity air, and the gas volume space velocity is 300L g cat -1 h -1 。
Example 2
(1) And (3) preparing a catalyst:
in the synthesis method of this example, only the ball milling time was changed to 0.5h, 1h, 3h, 10h and 20h, and the other preparation conditions were the same as in example 1. The catalyst obtained was designated as alpha/A-MnO 2 -T, wherein T is different ball milling times.
(2) Characterization of the phase/structure of the catalyst:
the catalyst obtained in this examplealpha/A-MnO as a chemical agent 2 The X-ray diffraction of T is shown in figure 6. According to XRD analysis, the prepared catalyst alpha/A-MnO 2 T is prolonged along with the ball milling time, and belongs to alpha-MnO 2 Is meant to mean delta-MnO during ball milling 2 From to alpha-MnO 2 After being transformed into amorphous intermediate phase, most of the intermediate phase is transformed into alpha-MnO 2 . Wherein the catalyst is alpha/A-MnO 2 -3 contains a large amount of amorphous manganese oxide and alpha-MnO 2 And forming a phase interface.
(3) The catalyst obtained in this example was alpha/A-MnO 2 -T catalytic performance test:
the change in catalytic performance of the catalyst at different temperatures (see FIG. 7) indicates that alpha/A-MnO 2 The activity of the formaldehyde catalytic oxidation is improved along with the extension of the ball milling time of the T catalyst; when the ball milling time exceeds 3 hours and reaches 10-20 hours, the formaldehyde catalytic activity is not improved any more and is slightly reduced. Wherein alpha/A-MnO 2 The catalyst-3 has excellent catalytic activity, and can completely catalyze and oxidize 120ppm of formaldehyde into CO at 80 DEG C 2 And H 2 O shows that the catalyst has better low-temperature catalytic activity; in addition, it shows a high catalytic reaction rate (0.21. Mu. Mol m -2 min -1 ) The activity of the catalyst is superior to that of most of the currently reported manganese-based non-noble metal catalysts. Formaldehyde catalytic oxidation reaction conditions: the raw material is a mixture of 120ppm formaldehyde and high-purity air, and the gas volume space velocity is 200L g cat -1 h -1 。
Example 3
(1) And (3) preparing a catalyst:
in the synthesis method of this example, the ball-to-material ratio was changed to 10: 1. 100:1 and 200:1, the remaining preparation conditions were identical to those of example 1. The catalyst obtained was designated as alpha/A-MnO 2 -R, wherein R is different ball to material ratio.
(2) Characterization of the phase/structure of the catalyst:
the catalyst obtained in this example was alpha/A-MnO 2 The X-ray diffraction of R is shown in FIG. 8. According to XRD analysis, delta-MnO can be realized with different ball material ratios 2 To alpha-MnO 2 Phase transition, wherein the catalyst alpha/A-MnO is prepared 2 -R ball-following-material ratioIncrease, belonging to alpha-MnO 2 A larger ball-to-material ratio means a higher mechanical strength and thus accelerates the phase transition process in ball milling.
(3) The catalyst obtained in this example was alpha/A-MnO 2 -R catalytic performance test:
the change in catalytic performance of the catalyst at different temperatures (FIG. 9) indicates that alpha/A-MnO 2 The activity of the R catalyst in the catalytic oxidation of formaldehyde is related to the sphere ratio, when the sphere ratio is 100: the optimum 1, while too low or too high a ball-to-charge ratio is detrimental to the improvement of formaldehyde catalytic activity. Wherein alpha/A-MnO 2 The catalyst-100 can completely catalyze and oxidize 120ppm of formaldehyde into CO at 80 DEG C 2 And H 2 O shows that the catalyst has better low-temperature catalytic activity; the activity of the catalyst is superior to that of most of the currently reported manganese-based non-noble metal catalysts. Formaldehyde catalytic oxidation reaction conditions: the raw material is a mixture of 120ppm formaldehyde and high-purity air, and the gas volume space velocity is 200L g cat -1 h -1 。
Comparative example 1
(1) And (3) preparing a catalyst:
target catalyst delta-MnO 2 -preparation of BM (BM is ball milling method): in delta-MnO 2 For the precursor ball milling, the ball milling time was changed to 1h only, and the other preparation conditions were the same as in example 1. The target catalyst is named delta-MnO 2 -BM。
Reference sample alpha-MnO 2 -preparation of BM: in alpha-MnO form 2 For the precursor ball milling, the ball milling time was changed to 1h only, and the other preparation conditions were the same as in example 1. The target catalyst is named as alpha-MnO 2 -BM。
Reference sample beta-MnO 2 -preparation of BM: 0.1g commercial beta-MnO is taken 2 Ball milling was performed for 1h, and the remaining ball milling conditions were identical to those of example 1. The obtained target catalyst is named as beta-MnO 2 -BM。
(2) Characterization of the phase/structure of the catalyst:
the X-ray diffraction of the catalyst obtained in this example is shown in FIG. 10. According to XRD analysis, delta-MnO 2 After ball milling, obvious phase change behavior occurs, and alpha-MnO 2 And beta-MnO 2 No phase change phenomenon after ball milling treatment.
(3) The catalyst obtained in this example was tested for catalytic performance:
the variation of the catalytic performance of the catalyst at different temperatures (fig. 11) shows that the activity of the catalytic oxidation of formaldehyde is related to the crystal form of the precursor. delta-MnO 2 BM catalysts exhibit excellent formaldehyde-catalyzing activity compared to reference samples, and can completely catalyze the oxidation of 120ppm formaldehyde to CO at 100 DEG C 2 And H 2 O shows that the catalyst has better low-temperature catalytic activity; the activity of the catalyst is superior to that of most of the currently reported manganese-based non-noble metal catalysts. Formaldehyde catalytic oxidation reaction conditions: the raw material is a mixture of 120ppm formaldehyde and high-purity air, and the gas volume space velocity is 200L g cat -1 h -1 。
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (4)
1. Use of a heterogeneous junction manganese oxide catalyst in the catalytic oxidation of formaldehyde, characterized in that the heterogeneous junction manganese oxide catalyst is prepared by the following method:
MnO is added to 2 Ball milling is carried out in an air atmosphere to prepare the heterogeneous manganese oxide catalyst; the MnO 2 Is delta-MnO 2 The method comprises the steps of carrying out a first treatment on the surface of the The ball milling time is 0.5-20 h; the rotation speed of the ball milling is 50-1200 rpm; the ball-milling ball material ratio is 10:1-200:1;
the delta-MnO 2 The preparation of the composition comprises the following steps: dissolving potassium permanganate and manganese salt in water, performing hydrothermal reaction after ultrasonic and stirring, cooling to room temperature after the reaction is completed, and cleaning and drying the obtained precipitate to obtain delta-MnO 2 ；
The manganese salt refers to MnSO 4 、Mn(NO 3 ) 2 、MnCO 3 、Mn(CH 3 COO) 2 At least one of (a) and (b); the super-gradeThe sound time is 1-2 hours; the stirring time is 0.5-2 hours; the cleaning is to clean with ultrapure water and absolute ethyl alcohol respectively; the concentration of the potassium permanganate added into water is 0.012-0.03M, and the concentration of the manganese salt added into water is 0.002-0.005M; the temperature of the hydrothermal reaction is 140-180 ℃ and the time is 8-16 h;
the heterogeneous junction manganese oxide catalyst consists of amorphous phase manganese oxide and alpha-MnO 2 Composition; the amorphous manganese oxide and alpha-MnO 2 The phase interface of (C) is a homogeneous heterogeneous junction.
2. The use according to claim 1, wherein the ball milling time is 3 hours; the rotation speed of the ball milling is 600rpm; the ball-milling ball-material ratio is 100:1.
3. The use according to claim 1, wherein in the ball milling process, the ball mill is at least one of a planetary ball mill, a shimmy ball mill and a vibratory plasma ball mill, and the ball milling tank and the grinding balls are at least one of stainless steel, agate, zirconia and polytetrafluoroethylene.
4. The use of claim 3, wherein the homoheterogeneous junction interface contains oxygen vacancies.
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